a) Field of the Invention
The present invention relates to an I-shaped wooden beam of improved structure. More specifically, it relates to a wooden beam comprising two elongated chords connected to opposite ends of at least one joining member, wherein each of the chords is made of two pieces of wood that are rigidly connected to each other and to the joining member(s) so as to form a unitary structure of I-shape.
The invention also relates to a process for manufacturing a wooden beam having such an improved structure.
In the following description and claims, the word xe2x80x9cbeamsxe2x80x9d must be interpreted as encompassing any kind of construction elements which may also be called xe2x80x9cjoistsxe2x80x9d, xe2x80x9cgirdersxe2x80x9d, xe2x80x9craftersxe2x80x9d, xe2x80x9cstudwoodxe2x80x9d, xe2x80x9cjoined studwoodxe2x80x9d, xe2x80x9claminated studwoodxe2x80x9d, xe2x80x9cframing timbersxe2x80x9d, xe2x80x9ctrussesxe2x80x9d and xe2x80x9croof trussesxe2x80x9d in the construction industry.
b) Brief Description of the Prior Art
Wooden beams of I shaped structure are well known and commonly used in the construction industry. They basically comprise two elongated chords (sometimes also called xe2x80x9cflangesxe2x80x9d) that extend in parallel relationship, and at least one joining member extending between the chords. In practice, the at least one joining member may consist of a web extending over the full length of the beam (see, for example, U.S. Pat. Nos. 4,456,497; 4,715,162 and 5,323,584). Alternatively, it may consist of a plurality of struts that extend perpendicularly with respect to the chords or, preferably, at an angle with respect to the chords and with respect to each other (see, for examples, U.S. Pat. Nos. 3,452,502 and 5,664,393). In all cases, the web or struts have opposite ends that are rigidly connected to the chords to form the requested, I-shaped unitary structure.
If such I-shaped wooden beams are of a great interest and presently used on a large scale in the construction industry, they nevertheless are known present two basic drawbacks.
The first one is their manufacturing costs that may be high when, as is of common practice, each of the chords is made of a xe2x80x9cnaturalxe2x80x9d, one-piece lumber having a 2xe2x80x3xc3x973xe2x80x3 or 2xe2x80x3xc3x974xe2x80x3 cross-section. Such a one-piece lumber must indeed be cut in a tree log and processed to be connected to the joining member(s). It must thereafter be connected to the joining member(s). All these steps are expensive because of the cost of xe2x80x9cnaturalxe2x80x9d wood and the time required to cut logs into lumbers of suitable size and to subsequently connect of such lumbers to the joining member(s) to obtain the requested I-shaped beam.
The second drawback of the I-shaped wooden beams presently in use is their stability over the time. Indeed, the lumbers forming the chords are made of material wood that is known to absorb moisture and be subject to warping.
To tentatively get rid of these two drawbacks, it has already been suggested to manufacture I-shaped wooden beams with chords and optionally joining member(s) made of xe2x80x9cengineeredxe2x80x9d lumbers, like those known as xe2x80x9claminated strand lumbersxe2x80x9d, xe2x80x9claminated veneer lumbersxe2x80x9d, xe2x80x9cparallel strand lumbersxe2x80x9d and xe2x80x9cglued laminated timbersxe2x80x9d (see, for further information on such engineered lumbers, columns 1 to 3 of U.S. Pat. No. 6,012,262). The advantages of such beams are that (1) their chords need not be cut from a tree log and are thus much less expensive to manufacture and (2) since the chords are made of different laminated components, they are less subject to deformation over the time, especially in the presence of moisture. In connection with point (1), it can be appreciated that engineered lumbers are quite easy to manufacture and the availability of such lumbers of any dimension is therefore much higher than the availability of natural lumbers of the same dimension.
As examples of I-shaped wooden beams with chords made of engineered lumbers, reference can be made to the above U.S. Pat. No. 6,012,262 and its Canadian counterpart No. 2,199,903. Reference can also be made Canadian patent Nos. 701,065; 1,065,116; 1,182,266; 1,196,169; 1,279,972 and 2,133,776.
An object of the present invention is to provide I-shaped wooden beam wherein each of chords is made of two pieces of natural wood that are rigidly connected to each other and to the joining member(s).
More specifically, each of the chords is made of two pieces of wood having adjacent surfaces that are in contact and extend in parallel relationship with respect to the at least one joining member over the corresponding opposite end thereof. The two pieces of wood also have tongues and grooves positioned close to their adjacent surfaces and sized to match with opposite tongues and grooves made on the corresponding opposite end of the at least one joining member. In use, the pieces of wood are rigidly connected to each other and to the at least one joining member preferably by gluing, so as to form the requested unitary structure of I-shape.
The I-shaped wooden beam according to the invention is of improved structure as compared to the existing beams whose chords are each made of a one-piece lumber. Indeed, the beam according to the invention is much less subject to wasping since each of its chords is made of two pieces that are connected to each other preferably by gluing, and thus  less than  less than behaves greater than  greater than  like a laminate.
The beam according to the invention is also easier to manufacture since the pieces forming chords are half of the size of the conventional chords and thus easier to cut.
Furthermore, the beam according to the invention is easier to assemble since the pieces forming its chords are shaped to  less than  less than fit  greater than  greater than  onto the ends of the joining member(s), thereby making their connection much easier to carry out.
Moreover, the structural strength, rigidity and resistance of the beam according to the invention are excellent since the connection of the opposite ends of the joining member(s) to the chords is achieved by means of tongues and grooves. Therefore, even if some of the glue or other means used to connect the pieces and joining member(s) together is missing or removed accidentally over some of the length of the beam, the connection will nevertheless remain strong, efficient and safe.
When use is made of glue for assembling the pieces of wood and joining member(s) together, the wooden beam according to the invention is preferably manufactured by:
(a) positioning the pieces of wood that extend on a same side of both chords, in a shaped apart, parallel relationship onto a flat surface;
(b) applying a layer of glue onto the tongues, grooves and surfaces of the pieces positioned in step (a);
(c) positioning and pressing the at least one joining member onto the pieces onto which the glue was applied in step (b) to cause the tongues and grooves made on one side of the opposite ends of said at least one joining member to snap and fit into the tongues and grooves of the spaced apart pieces;
(d) applying a layer of glue onto the other tongues and grooves made on the other sides of the at least one joining member; and
(e) positioning and pressing the other pieces of wood of the chords to cause their tongues and grooves to snap and fit into the other grooves and tongues of the at least one joining member, and the surfaces of said other pieces to come into contact and be glued to the adjacent surfaces of the pieces positioned in step (a).
This process is another important object of the invention which is claimed per se hereinafter.
The invention and its numerous advantages will be better understood upon reading the following non-restrictive description of two preferred embodiments thereof made with reference to the accompanying drawings.